Process of manufacturing boric acid.



UNITED STATES PATENT OFFICE.

OTTO BEST, DAGGETT, CALIFORNIA.

PROCESS OF MANUFACTURING BORIC ACID.

Specification of Letters Patent.

Patented Dec. 4, 1906.

Application filed. June 18,1206- Serial No. 322,237.

To all whom it may concern:

Be it known that I, OTTo BEST, a citizen of the United States, residing at Daggett, in the county of San Bernardino and State of'Cali fornia, have invented new and useful Imrovements in Processes of Manufacturing oric Acid, of which the following is a specification'.

This invention relates to a process for preventing the formation of gelatinous silica in a working borosilicates into boric acid.

ture, dependent upon the prevailing condi- The aim of the present invention is to tions. prevent the separation of this gelatinous silica, and thus render this source of borate more easily available for the manufacture of boric acid.

The gelatinous silica will be hereinafter designated as jelly.

4 The process now used in California to manufacture boric acid from these boro'silicates ore suspended in water sulfuric or sulfurous acid to release the boric acid fromthe borosilicates that are mostly combined with lime. Other suitable acids may be used to release the boric acid.

The boric and silicic acids may be combined with other bases, and, in varying amounts, other compounds may be present, such as calcium sulfate, calcium carbonate, and silicates of alumina, iron, magnesia, lime, &c.

At present the only compounds that need be considered are the borates and silicates.

Supposing that (for illustration) sulfuric acid is used to decompose the ore, the reactions now to be considered would be the following:

First, calcium borate plus sulfuric acid form calcium sulfate plus boric acid; second, calcium silicate (or any other silicate present and decomposable by acid) plus sulfuric acid form calcium sulfate (or other sulfate) plus soluble silicic acid. The mother-liquor that subsides from the muddy residue can be filtered or separated from the mud by settling or any other suitable process and holds in solution boric acid, varying amounts of silicic acid, and more or less salts, (sulfate of iron, alumina. magnesia, &c.) If the mother-liqtions.

uor is too weak, it is evaporated to crystallization, here in California by solar evapora-.

tion, or if strong enough heated and the boric acid crystals separated by cooling. After standing for a longer or shorter time or on evaporation jelly separates, this separation 1 taking place sooner or later, according to the amount of silicic acid in solution, the con-- centration of the liquor, the amount of impurities in solution, and many other condi- This jelly carries with itself what ever was present in the liquid before gelatinization, and naturally also the boric acid; but whenever this jelly is formed the common methods of extracting the boric acid from it are unavailable. This jelly is at present usually worked by evaporating it downto dryness to render the silicic acid insoluble and then extracting the boric acid from the now pulverulent material: This process is very slow and expensive and entails much loss of boric acid.

My improved process aims to prevent the formation of jelly, and thus avoid the loss of 1 time, labor, and material. l

The principle 'of this new process is to add I j to the solution containing boric acid and si- (mainly low grade) 1s to add to the ground licic acid such materials and chemical comthe silicic acid, thus precipitating the soluble silicic acid r and prevent the later formation of jelly. Just enough of this chemical compound must'be added to saturate and sep arate the silicic acid without combining with the boric acid. If intermediary borates are formed, they will be decomposed again so long as silicic acid is in the solutlon, as mostly all silicates are less soluble than the corresponding borates.

The process itself is carried out as follows: The borosilicate ore is ground, stirred up with water, and a sufiicient quantity of sulfuric or any other suitable acid is added to bring all the boric acid into solution. Varying amounts of silicic acid are then in solution also, I now add to this decomposed ore milk of lime, or I add the lime ground in the form of a fine powder. The added lime forms an insoluble compound with the soluble silicic acid and precipitates the same as calcium silicate, thus removing it from the li uor and preventing the later formation of jelly in the solution. Instead of lime any other base forming an insoluble compound with the silicic acid can be used, such as magnesia, oxide or hydroxids of barium,

IIO

. v lime, may be used. In the case of the caruble silicate of magnesia.

bonate, however, the reaction is very slow. Caustic lime, or in this case also caustic soda, potash, and carbonate of soda or potash, &c., can be used in combination with magnesia, iron, alumina, salts, &c. The reaction then is as follows, it'being supposed that in all cases sulfuric acid is used for decomposing the ore: If magnesia sulfate is used, We get, first reaction, magnesia sulfate plus caustic lime form calcium sulfate .plus magnesia hydroxid; second reaction, magnesia hydroxid plus soluble silicic acid form insol- These reactions of course go on simultaneously. In this case the hydroxid is freshly precipitated in a nascent state, and therefore readily combines with the soluble silicic acid.

For caustic lime any other base or carbonate that precipitates out the hydroXid, like caustic soda, potash, or in some cases the corresponding carbonates, &c., may be substituted. For magnesia sulfate any other sulfate or salt the base of which forms an insoluble compound with silicic acid may be used.

It is readily to be seen from the reactions given above that if magnesia or other salts are present in the water or are extracted from the ore by the sulfuric or other acid, which is always more or less the case, not only the soluble silicic acid is removed, but

these salts at the same time. This process, therefore, not only prevents the formation of jelly, but at the same time purifies the liquor and frees it of contaminating salts. Wherever and whenever such salts are in the mother-1i uor a correspondingly smaller quantity 0 these salts need be added, and in some cases none at all may be needed.

A third point has been attained by this new process. It is found that with this treatment the mud subsides and the liquor clears quicker, so that more and clearer liquor can be drawn off Wherever settling is used. This is of the greatest importance, particularly in the working of low-grade materials.

I claim 1. The process of making boric acid from borosilicateswithout the formation of jelly, which consists in decomposing the borosilicate with a suitable acid to release the boric acid, then adding a base to form an insoluble silicate, and then separating the liquor from the precipitated silicate, substantially as described.

2. The process of making boric acid from borosilicates without the formation of jelly, which consists in decomposing the borosilicates with a suitable acid to release the boric acid, then adding slaked lime in proportion to the silicic acid in solution, stirring to mix well and permit the lime to combine with the silicic acid, and separating the liquor from the precipitated silicate, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

OTTO BEST.

Witnesses:

T. S. VAN DYKE, D. S. VAN DYKE. 

